Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$97.73	13.647%	$111.0672	$111.07	$111.05	$111.10
Purchase #2	$112.32	9.608%	$123.1117	$123.11	$123.10	$123.10
Purchase #3	$188.56	3.823%	$195.7686	$195.77	$195.75	$195.80
Purchase #4	$50.89	8.696%	$55.3154	$55.32	$55.30	$55.30
Purchase #5	$162.33	6.250%	$172.4756	$172.48	$172.50	$172.50
Purchase #6	$114.89	11.785%	$128.4298	$128.43	$128.45	$128.40
Purchase #7	$130.42	6.569%	$138.9873	$138.99	$139.00	$139.00
7 purchase totals =	$857.14		$925.1556	$925.17	$925.15	$925.20